The present invention relates to a multi-point calibration method for imaging light and color measurement devices.
In contrast to the conventional spot light and color measurement systems, an imaging light and color measurement device is able to measure the magnitude and color of light for many different data points at one time. To accomplish this, the imaging light and color measurement device images all light visible to the camera onto a detector array comprising thousands or millions of individual detectors. Further, in conventional spot measurement techniques, measurements are made over only a small area of the display device under test. Therefore, traditional measurement comprises an average color or luminance measurement taken over a single area (and measured by means of a single detector). FIG. 1 shows the conventional spot measurement technique for measuring a display screen 10 with an array of individual light emitting areas to be measured. In FIG. 1, by shifting the spot measuring camera 12, each light emitting area is measured individually. Therefore, a long time is consumed for measuring a display device with multiple light emitting areas using the conventional spot measurement instrument.
In contrast, the imaging light and color measurement device images the light entering the camera onto thousands or millions of detectors (pixels) and therefore is able to acquire much more data without moving the measurement instrument, as in the case with the prior art spectroradiometer, calorimeter, or luminance meter. The primary advantage of the multi-point imaging light and color measurement system is the speed with which it can acquire thousands or millions of data points thereby giving a complete analysis of the color and brightness characteristics of the source of light.
A charge-coupled device (CCD) detector is a very broadly applied device for the imaging photometer/radiometer/colorimeter. The CCD-based imaging systems have been used as imaging light and color measurement devices to quantifiably measure luminance, illuminance and color coordinates of light sources, display systems, illumination systems or any sources of light. The CCD-based imaging system captures images of a scene (or device) to be analyzed for luminance or color. In the case of CIE 1931 color space, each pixel comprising the image may contain light which has different (x,y) chromaticity coordinates. In the case of photopic or radiometric measurements, each pixel may receive a different magnitude of optical radiation. In practice, the spectral responsivity of the imaging light and color measurement device does not exactly match the CIE x,y,z chromaticity matching functions or a photopic response curve or a flat radiometric response curve. Therefore, calibration is required.